Two doses (20 or 200 mg/kg) of crude marihuana extract were administered (p.o.) daily to pregnant rats either throughout gestation or during one of the three weeks of gestation. Control animals received vehicle administrations and were pair-fed to drug-treated animals in each of these groups. At birth, all offspring were removed from their biological mothers and were fostered to nondrug-treated surrogate mothers. Marihuana reduced food and water consumption and maternal weight gain during pregnancy. Pup weight at birth was reduced, and neonatal mortality was increased in offspring exposed during the last week of gestation or throughout gestation. Litter size, postnatal mortality, and weight at weaning were not significantly affected by drug treatment. Behavioral studies conducted thus far have revealed no differences between drug-treated animals and controls in shock avoidance or brightness discrimination learning or spontaneous alternation. We are currently conducting studies and analyzing data regarding water escape maze learning and Rotarod behavior.